This device is a compact device for exciting a waveguide with wideband circular polarization in both directions and with high purity of polarization. It enables a right and/or left circularly polarized wave to be generated in a waveguide having a section which may be square or circular, for example.
Such a device is intended for use in any waveguide radiating element requiring compact excitation in circular polarization from a transverse electromagnetic (TEM) line feed, e.g. a coaxial line, a three-plate line, or a microstrip line.
Prior systems for generating a circularly polarized wave in a waveguide from a TEM line are:
either systems constituted by a TEM line to waveguide transition together with a polarizer which gives rise to considerable bulk (with a typical length being greater than two wavelengths) for performance equivalent to the performance of a device in accordance with the invention; PA1 or else compact systems using a resonator at the end of a waveguide, but providing mediocre quality in terms of bandwidth and polarization purity and therefore incompatible with pure circular polarization as used in telecommunications frequency bands. PA1 to reduce bulk; and PA1 to increase the frequency band width for given values of matching and ellipticity. PA1 it is extremely compact, circular polarization is directed generated in this case from a TEM line over a length which is shorter than one wavelength; PA1 it is provided with longitudinal rear accesses, thereby enabling these accesses to be coupled without additional coaxial cables to a TEM power distributor for transmission and/or reception parallel to the section of the waveguide, at which location hybrid quadrature-imparting couplers may also be implanted; and PA1 it can be used with any circular polarization antenna where there is a problem of compactness or bulk for the polarization device.
An article by C. H. Chen, A. Tulintseff, and R. M. Sorbello entitled "Broadband two-layer microstrip antenna" published in IEEE 1984 (A.P.S. 8-1 "Antenna and propagation symposium" 1984) describes a broadband two-layer printed antenna that radiates freely. Such an antenna is characterized by two resonant frequencies. By exciting this antenna with two orthogonal modes at equal amplitude and quadrature phase, circular polarization operation is obtained.
In contrast, the object of the invention is to generate a right and/or left circularly polarized wave in a waveguide.